Just from his own reaction it seems like he may have not realizedWas the headpat really necessary? Everything else was pretty inline with normal friendships & with his character in general, but the headpat seemed extremely forced as a catalyst to push Hitotsuba over the edge.
This, as unnecessary drama as it is, MC giving that much attention to his (girl) friend while always rejecting Kaede is kinda fucked up. And if he gets that backpack for Nikaidou then he's officially the worst bf.It seems silly to blow up (cartoonishly) over a headpat, but I kinda get where she's coming from. Headpats may be relatively mild but they're still a public display of affection, and Yuya always pushing back against her PDAs but then casually giving it to another girl is kinda fucked up. A lot of Kaede's jealousy is irrational and she knows it, but then Yuya goes and makes it worse by actually doing something worth being jealous over. And while it's absolutely justifiable for Yuya to prioritize study over flirt-and-cuddle-time with his gf, it's still gonna hurt when she's clearly craving it so badly to assuage the jealousy.
And if he gets Nikaido that backpack but doesn't do something over-the-top for Kaede, that's going to be a HUUUUGE fuckup.